GASTROINTESTINAL HEMORRHAGE (2): Melena. Melena, the passage of black, tarry stools, usually implies blood loss greater than 500 ml originating anywhere between the oropharynx and the right hemicolon. Melena occurs most often, Melanocytic Lesions and Disorders of Pigmentation Obgyn Key Recognition of Melanocytes in Immuno Neuroendocrinology and Circadian Rhythms: Beyond the Conventional Melanin Synthesis Oral Melanotic Macule: Symptoms and Treatment Skinsight